1. Field of the Invention
The present invention relates to a ballistic aerosol marking apparatus and, more particularly to a gating method and apparatus for ballistic aerosol marking.
2. Background of the Invention
Ballistic Aerosol Marking (BAM) systems are known to eject particulate marking materials for marking a substrate. For example, U.S. Pat. No. 6,340,216 and U.S. Pat. No. 6,416,157, which are hereby incorporated by reference in their entirety, disclose a single-pass, full-color printer which deposits marking materials such as ink or toner. High speed printing either directly onto paper or a substrate or indirectly through an intermediate medium can be achieved using Ballistic Aerosol Marking (BAM) systems. An array or multiplicity of channels are provided in a print head through which a propellant stream is directed. Marking material or multiple marking materials may be introduced into the channel and the propellant stream to be mixed and deposited on the substrate. When using particulate or solid based marking material, the material must be metered through an aperture into the channel from a reservoir. An example of moving and metering the marking material is also disclosed in U.S. Pat. No. 6,290,342 which is hereby incorporated by reference in its entirety. A plurality of electrodes are provided with an electrostatic travelling wave to sequentially attract particles to transport them to a desired location. At higher resolutions, only very low agglomeration, or powdery toner can be metered through the smaller apertures. When using such smaller apertures and low agglomeration toner, problems encountered include clogging and surface adhesion of the marking material to the walls of the channel, aperture or metering device. Additional problems are encountered in precisely metering the material to be deposited in order to effectively mix colors or achieve proper gray scale on deposition of the marking material. Accordingly, there is a desire to provide a Ballistic Aerosol Marking (BAM) system capable of precisely metering marking material without clogging or surface adhesion issues.